455 performance... what next?

Guys,

I've got a 455 that runs good and getting about 14.4 in the quarter mile. I'm guessing it weighs around 3750 with driver. I'd like to do a little better in HP and quarter mile without ripping the entire engine apart for the next 6-7 years. Here's what I know about the motor:

-1972 block WF358
-1970 heads 1231786. Should be higher compression, 10.5:1
-1971 intake manifold, 4 bbl
-1970 quadrajet rebuilt with better internals and CK secondary metering rods
-possible cam, competition cams 268H, which I'm told is a tiny cam
-stock exhaust manifolds
-2.25" OD dual exhaust
-stock torque converter
-points distributor, with correct mechanical advance.

So can I just put in a better cam and headers and/or port out the exhaust manifolds to get close to 400 hp? The cam issue has come up as being tiny and also, with the 1970 heads, possibly too much compression in this set up which is why i may have had pinging issues until I added a little race gas.

I'm not looking for a 500+ HP car right now. Happy with 400 hp for the next 7 years or so or maybe forever.

 

Very little gains with exhaust manifold porting compared to the amount of work involved. Swap in some headers and see what it'll do. I would imagine you would be surprised how it will run with the single pattern Comp 268 cam. That cam cries out for headers, it was designed for a sbc engine and ground on a BBB cam core that has the same amount of intake duration as exhaust duration.

Without having a split pattern duration cam with emphasis on the ex. side in a BBB with factory heads is choking the exhaust off and slowing you down.

You didn't mention what trans and rear gear you have either.



Derek

 

I agree with the above. What heads? Small or large valve? Sounds like the exhaust is kind of small also.

 

No where near 10.5 to 1 compression, closer to 9.2

Probably have to much timing in it or the stop bushing is gone and it's over advancing

Boltons on such a mild engine won't net you a whole lot , but start with a 2.5in exhaust kit and headers , manifolds aren't holding it back to awful much IMO , but headers, exhaust, B4B, good working Carb, 2500 stall all done at once will make you feel better about the $'s spent

 

Thanks!

I got a TH400 transmission
3.31 gears in differential

I like the idea of a stock look, which is why I'm having a hard time parting with stock exhaust manifolds and want to keep a stock intake for now.

Distributor and timing is perfect today. I worked this issue out last year with Larry and ended up buying the correct distributor as even with a bushing I had too much advance.

 

No idea what valves are in the heads. The guy that did the motor is deceased.

 

I would just do the 2.5 exhaust first and converter, then make sure what ever Carb is on it is dialed in.

Sometimes you gotta just dig into to it to find the power tho

 

Then do a cam swap and get the single pattern cam out of there and put a cam in it that was actually designed for a Buick engine that has a split pattern duration.And match the new cam with a new converter and you should be good to go.

With factory un-ported heads and factory exhaust manifolds I think the 2 1/4" ex. pipe is good enough for now, maybe add an X pipe to your system to assist with scavenging. Just don't get carried away with your new cam choice, TA-284 or the TA-212? Stay with a somewhat mild cam for what you have.

What makes you think you have 10.5:1 compression? If its a factory '72 short block with '70 heads, that won't make it go that high, like hugger said, probably more like 9 something to 1 if that's what it is.


Derek

 

The 10.5:1 was pulled out of the air or out of my rear......
I was thinking it was higher compression with the pinging at WOT and 1970s heads.

 

Leave the engine alone for now. Eventually, you'll get to 400 hp, but I doubt you're there already.

Begin with chassis development to reduce quarter-mile times. What tires, what springs, what trailing arms/traction devices are you using? Posi? Do you care about handling on the street?

Your torque converter is not optimum. A switch-pitch might be nice; or a QUALITY modern converter that flashes high but doesn't have much slip at cruise would be good.

Your exhaust system stinks.

3.31 rear gears are a good compromise for street/strip, but deeper gears would drop your quarter-mile times.

When you finally get to engine development:
Needing race gas to eliminate ping sounds suspicious to me. More investigation needed. Maybe fuel-curve, maybe ignition advance issues. How hot does the engine run at cruise? What is the quench/squish distance?

What valve springs do you have?

What is the cranking compression?

How much cylinder leakage?

 

I'm nowhere near 400hp now. I have posi traction. I have Mickey Thompson street ETs on the back at the track. 255/60r15. It has air bags. No other traction devices on it.

I want a street car first. Maybe 3 times a year at the track. Not interested in radical changes.

The engine runs very good while cruising and I think at about 18o or 185. Cranking compression is 165 to 175 with mostly 170 psi. I haven't checking leaking but during the cranking compression test, it didn't drop from what I recall while I was fiddling around.

I don't have any other internal data on the engine other than that. Valve springs.... no idea. Just pictures

 

What is your 60' time and mph when you ran the 14.4?

 

2.1 seconds and 93 mph
And I do like the 3.31 gears as a street/strip compromise.

 

Get it breathing with headers and work on the 60'..........2 tenths off the 60' and you'll be running high 13's

 

With only 93 mph it physically couldn't 60' much better,...

You need more power

You may could get some high 1.80s but with the power you have available that's it

 

Yeah, its that cam. The Comp 268 runs out of steam FAST, he is lucky if it can rev much past 4,000! Headers would help but probably not to much.

That cam with its single pattern design on a sbb 350 runs out of air around 4,600 with stock manifolds on it, put a set of headers on and it can pull up to 5,200, I would imagine the air would back up even faster in a BBB using manifolds with the same grind.

Different cam is what I would do first if I wanted to keep ex. manifolds so the dam thing could breath a bit better through to the traps.

Do you have a tach and if so at what RPM do you shift at?


Derek

 

I would upgrade your fuel system first. specifically your fuel pump. are you at least running a stage 1 pump with the deep bowl? if its a stock, non stage pump I'm sure you're starving for fuel.

 

Thanks.
I have a tach. I don't recall if I shifted at 4700 or 5000. I know for sure it was never over 5500.

 

Yep, stage 1 pump installed last year. It never noses down at wide open throttle. Fuel pressure never below 5 psi. My memory tells me more like 5.5 minimum.